One of the most powerful Ukrainian rebel leaders has confirmed for the first time that pro-Russian separatists were in possession of the missile system that U.S. intelligence analysts claim is responsible for shooting down Malaysia Airlines flight MH17 last Thursday.

Alexander Khodakovsky, the commander of the Vostok Battalion, admitted to Reuters Wednesday that anti-Ukrainian forces did have the Soviet-made Buk missile system at the time the plane was downed and, while he believes the Buk was smuggled into hiding in Russia, the weapon likely originated in Russia in the first place. The Donetsk People’s Republic, the main rebel group in the region, has consistently denied having the firepower necessary to take down the plane, although there are various separatist groups fighting against Ukrainian military forces in this disputed region of eastern Ukraine.

“I knew that a Buk came from Luhanski. At the time I was told that a BUK from Luhanski was coming under the flag of the LNR,” Khodakovsky told Reuters, referring to the Luhansk People’s Republic, which operates in the region connected to Donetsk, where the plane when down.

“That Buk I know about. I heard about it. I think they sent it back. Because I found out about it at exactly the moment that I found out this tragedy had taken place,” he went on. “They probably sent it back in order to remove proof of its presence.”

Previous reports have indicated that the rebel groups fighting in Ukraine have received weapons and training from the Russian military. They are, in many cases, even led by Russian citizens who have provided instructions on how to operate the often-complicated weapons machinery. Even so, Khodakovsky maintained, Ukrainian officials are responsible for the crash and should be held accountable.

“The questions is this: Ukraine received timely evidence that the volunteers have this technology, through the fault of Russia. It not only did nothing to protect security, but provoked the use of this type of weapon against a plane that was flying with peaceful civilians,” he told Reuters.

“They knew that [the Buk] would be deployed there, and provoked the use of this Buk by starting an air strike on a target they didn’t need, that their planes hadn’t touched for a week. And that day, they were intensively flying, and exactly at the moment of the shooting, at the moment the civilian plane flew overhead, they launched air strikes. Even if there was a Buk, and even if the Buk was used, Ukraine did everything to ensure that a civilian aircraft was shot down.”

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